Structural Analysis and Evaluative Study of the Architectural Design of Soltaniyeh Dome: Study of Restoration Interventions Using Numerical Modeling and Finite Element Analysis Running Title: Structural Analysis and Evaluative Studies of the Soltaniyeh Dome

Abstract

The Soltaniyeh Dome in Zanjan Province is one of the most important and prominent architectural works of the Ilkhanid period, which was built in 1302 AD by order of Sultan Mohammad Khodabandeh (Oljaito) in the city of Soltaniyeh. This dome is not only a symbol of the grandeur and splendor of Islamic architecture during the Ilkhanid period, but also, due to the intelligent combination of Iranian architectural elements and technical innovations, has become a model for architectural works after it. The main goal of this research is to analyze the structural design of the Soltaniyeh Dome, focusing on the impact of conservation interventions, especially the concrete ring, on structural stability and the reinterpretation of its tangible and intangible values ​​in the architecture of the Ilkhanid period. To achieve this goal, the present research seeks to answer the following questions: What is the impact of the concrete ring intervention on the structural behavior of the Soltaniyeh Dome? How can structural design analysis and structural modeling help to better understand the tangible and intangible values ​​of the architecture of the Soltaniyeh Dome? What lessons can be learned from the experience of the Soltaniyeh Dome conservation interventions for the conservation of other historical monuments? This research, by combining analytical methods, numerical modeling, and historical studies, seeks to provide comprehensive answers to the aforementioned questions. The results of this research, in addition to increasing knowledge in the field of architectural heritage conservation, can help improve conservation policies and methods in Iran and the world. This research is based on three main theoretical pillars: a- Ne'arsh in Iranian historical architecture (combination of structure and art), b- Valorization of cultural heritage (tangible and intangible), and c- Engineering of historical structures (behavior of dome shells and adaptive conservation). All data used in this research, including architectural drawings and technical reports, were collected through existing documentation and field visits. Field visits included precise measurements of the dome dimensions, recording the current condition of structural components, and recording images of the building. Also, for numerical analysis and modeling, ABAQUS software was used, which is specially suitable for simulating structural behavior and complex numerical analysis. In this research, numerical modeling of the Soltaniyeh Dome against different loads was carried out using ABAQUS software in order to investigate its structural behavior and the effect of the concrete ring intervention. The results of these analyses, including the effect of this intervention on the distribution of stresses and strain changes, were specifically examined. These results were compared with each other based on field data and historical documents, and the effects of the concrete ring intervention on the structural stability of the Soltaniyeh Dome were evaluated. The results of this research show that the initial design of the Soltaniyeh Dome, due to the use of precise design principles, has high stability. Past conservation interventions, especially the use of concrete rings, have not had much impact on improving structural performance under gravity conditions, but when exposed to seismic forces, they can lead to new damage. These findings emphasize that in restoration interventions of historical monuments, more accurate structural analyses should be performed and methods should be used that have the least negative impact on the stability and authenticity of the building. Future studies can provide a deeper understanding of the structural and restoration challenges of the Soltaniyeh Dome and help optimize conservation methods for this world heritage site. The results of this study fully confirm the hypotheses raised at the beginning of the study. The Soltaniyeh Dome is well able to withstand and distribute loads under normal gravity loads, given its geometric design and material properties. The hypothesis that the concrete ring had no significant effect on the dome's performance against gravity loads was also confirmed. In the context of seismic loads, the analyses showed that the presence of the concrete ring could have a negative effect under seismic conditions and prevent the dome from naturally flexing. This emphasizes the importance of designing appropriate protective interventions against dynamic loads. Overall, the interpretation of the findings of this study clearly shows that the Soltaniyeh Dome, as a masterpiece of Islamic architecture, performs well in response to gravity loads, but suffers from problems against seismic forces, especially with the presence of ineffective restoration interventions such as concrete tensioning. In addition to providing more accurate information about the structural behavior of the dome, these findings are an important step towards evaluating and critiquing past restoration approaches. One of the most important innovations of this research is the use of advanced simulations to model the behavior of the dome under different conditions and provide more accurate analyses of the effects of restoration interventions. These analyses will help researchers and restoration professionals to carry out conservation and retrofitting interventions more accurately in the future and prevent potential damage.